[llvm] [VPlan] Add new VPInstruction ocpode for header mask. (PR #89603)

[via llvm-commits]

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@@ -1202,52 +1187,23 @@ static VPActiveLaneMaskPHIRecipe *addVPLaneMaskPhiAndUpdateExitBranch(
   return LaneMaskPhi;
 }
 
-/// Collect all VPValues representing a header mask through the (ICMP_ULE,
-/// WideCanonicalIV, backedge-taken-count) pattern.
-/// TODO: Introduce explicit recipe for header-mask instead of searching
-/// for the header-mask pattern manually.
-static SmallVector<VPValue *> collectAllHeaderMasks(VPlan &Plan) {
-  SmallVector<VPValue *> WideCanonicalIVs;
-  auto *FoundWidenCanonicalIVUser =
-      find_if(Plan.getCanonicalIV()->users(),
-              [](VPUser *U) { return isa<VPWidenCanonicalIVRecipe>(U); });
-  assert(count_if(Plan.getCanonicalIV()->users(),
-                  [](VPUser *U) { return isa<VPWidenCanonicalIVRecipe>(U); }) <=
-             1 &&
-         "Must have at most one VPWideCanonicalIVRecipe");
-  if (FoundWidenCanonicalIVUser != Plan.getCanonicalIV()->users().end()) {
-    auto *WideCanonicalIV =
-        cast<VPWidenCanonicalIVRecipe>(*FoundWidenCanonicalIVUser);
-    WideCanonicalIVs.push_back(WideCanonicalIV);
-  }
-
-  // Also include VPWidenIntOrFpInductionRecipes that represent a widened
-  // version of the canonical induction.
-  VPBasicBlock *HeaderVPBB = Plan.getVectorLoopRegion()->getEntryBasicBlock();
-  for (VPRecipeBase &Phi : HeaderVPBB->phis()) {
-    auto *WidenOriginalIV = dyn_cast<VPWidenIntOrFpInductionRecipe>(&Phi);
-    if (WidenOriginalIV && WidenOriginalIV->isCanonical())
-      WideCanonicalIVs.push_back(WidenOriginalIV);
-  }
-
-  // Walk users of wide canonical IVs and collect to all compares of the form
-  // (ICMP_ULE, WideCanonicalIV, backedge-taken-count).
-  SmallVector<VPValue *> HeaderMasks;
-  VPValue *BTC = Plan.getOrCreateBackedgeTakenCount();
-  for (auto *Wide : WideCanonicalIVs) {
-    for (VPUser *U : SmallVector<VPUser *>(Wide->users())) {
-      auto *HeaderMask = dyn_cast<VPInstruction>(U);
-      if (!HeaderMask || HeaderMask->getOpcode() != Instruction::ICmp ||
-          HeaderMask->getPredicate() != CmpInst::ICMP_ULE ||
-          HeaderMask->getOperand(1) != BTC)
-        continue;
-
-      assert(HeaderMask->getOperand(0) == Wide &&
-             "WidenCanonicalIV must be the first operand of the compare");
-      HeaderMasks.push_back(HeaderMask);
+static VPValue *getOrCreateWideCanonicalIV(VPlan &Plan,
+                                           VPInstruction *HeaderMask) {
+  VPValue *Op = HeaderMask->getOperand(0);
+  if (isa<VPWidenIntOrFpInductionRecipe, VPScalarIVStepsRecipe>(Op))
+    return Op;
+  // Check if there is a wide canonical IV that can be re-used.
+  if (auto *CanIV = dyn_cast<VPCanonicalIVPHIRecipe>(Op)) {
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ayalz wrote:

CanIV is now useless.

Is the check needed - does Op need to be a VPCanonicalIVPHIRecipe for the following search and replace to apply?

https://github.com/llvm/llvm-project/pull/89603